Preliminary work undertaken on this project shows that enamel proteins are found on the roots of mouse molar teeth. Work which is currently in progress indicates that these proteins are found in the epithelial rests of Malassez associated with human teeth. Experiments conducted with inbred strains of mice indicate that enamel proteins are autoantigens, and moreover that functional T-cells are required for elicitation of this autoimmune response. A hypothesis which was constructed to possibly account for rapidly progressive periodontitis which is refractory to treatment stated that: Enamel proteins are located in a thin layer between the dentin and cementum of human teeth. During the course of inflammation associated with bacterial plaque antigens, some of the overlaying cementum becomes resorbed, thus exposing the enamel proteins. The enamel proteins would then serve as an endogenous store of antigen, resulting in an auto-immune component in the disease process. Since we have not found enamel proteins in the predicted location on human teeth (although we have found enamel proteins between cementum and dentin on rodent molar teeth), it is unlikely that the hypothesis is correct. We are therefore undertaking studies to determine the relative contribution of various species of oral bacteria to eliciting local (gingival) immune responses at different histopathological stages of the disease process.